I don't understand the issue of man power? At the moment the RN is manning both Lusty and Ocean. Both these ships will be replaced by the QE class, of which only one will be operational at any time.
Type 42s continue to be replaced by the less head count hungry 45s, and in the next decade the 23s will in turn be replaced by 26s - which will no doubt also show head count efficiencies. But the 1SL has already said, while he has enough to man 1 active CVF, if the UK decided to run them concurrently, he would need an increase. It ain't going to happen though. The reality will be that 1 CV and 1 LPD will be held in deep reserve, and rotated out to cover long refit periods. This should extend the lives of both classes of ships. I believe that CVF is built to last 50 years, so they might be still showing the flag beyond your children's lives. Not bad for £6bn!